CHICAGO--(BUSINESS WIRE)--Merck (NYSE:MRK), known as MSD outside the United States and Canada, today announced the first presentation of data evaluating pembrolizumab (MK-3475), Merck’s investigational anti-PD-1 antibody, as initial therapy in patients with PD-L1 positive, advanced non-small cell lung cancer (NSCLC). In previously-untreated patients, the objective response rate (ORR) (confirmed and unconfirmed) with pembrolizumab as a single-agent (monotherapy) was 47 percent by investigator-assessed, immune-related response criteria (irRC) (n=21/45: 95% CI, 32-62) and 26 percent by centrally evaluated RECIST v1.1 (Response Evaluation Criteria in Solid Tumors) (n=11/42: 95% CI, 14-42). In evaluable patients who had measurable disease with one post baseline scan, 80 percent demonstrated tumor shrinkage as measured by centrally evaluated RECIST criteria (n=28/35). The median duration of response has not been reached, with some patients continuing on treatment with pembrolizumab as monotherapy for at least one year.